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[Q] Can I do a /data backup then unlock bootloader?

As the Title states, I'd like to know if I can do a data backup via the stock Android Recovery, since I heard that Unlocking Bootloader would lead to a data erase. So I was wondering if whether I could restore the backup after unlocking bootloader and have my data intact (It ain't my phone)

I'm not sure but you can make a backup and place it on a computer and then unlock the boot loader and restore it when you are done with all the things.

Use carbon/helium.

So I see

Prevent data wipe on unlock

So i have a nexus 5 with a broken inoperable screen. Mtp mode as well as usb debugging is not enabled. Need the stuff from internal storage. Thinking if i unlock the bootloader in fastboot then immediately reboot to the bootloader after unlocking then using fastboot to boot a custom recovery, i should still have my data. Which i can then backup through nandroid backup or adb. (Since the wipe is done during first os boot, i believe.) Can anyone confirm? I don't wanna unlock then lose my stuff but I'm trying to avoid screen raplacemnt at all costs.
TIA

How secure Galaxy S6 bootloader is?

I am wondering about security of Galaxy S6 (not Edge) bootloader. The goal is to prevent users to do any major modifications to the phone (boot custom ROMs, for example), so I have a few questions about this phone:
1. Some versions are unlocked by default, can I lock bootloader manually (and restore OEM Unlock option if missing)?
2. How secure is option "OEM unlock" in Debugging mode? If disabled, can user unlock bootloader in recovery mode with 3rd party tools or not?
3. Can Samsung phones be somehow secured to prevent OS reinstallation?
The best goal we may want to archieve is to prevent unauthorised persons to do anything with the phone without knowing the PIN, so the phone cannot be flashed with the new ROM and used again.
Thanks.

1-You can't
2-It should pretty secure on other brands but I'm not sure for Samsung devices.
3-Only Samsung can adjust it on bootloader.
On S6, bootloader doesn't allow custom (modded) bootloader flash, custom (modded) modem flash or repartition in any situtation.
But, if you turn on Google factory reset protection or Samsung factory reset protection, any root proccess or any custom (modded) kernel, any custom (modded) recovery, or custom (modded) system image flash proccess will be denied by bootloader. FRP is more powerful than OEM Unlock.

Bootloader unlocking, relocking and security aspects

I installed a custom operating system (LineageOS for microG) and a custom recovery environment (TWRP) into my Oneplus 3T recently. The bootloader had to be unlocked to do this of course.
As far as I understand, locking it again would prevent the phone from booting as custom operating systems are not signed with the phone manufacturer's keys. This also applies to custom recoveries, is that correct?
What are the exact security drawbacks of having an unlocked bootloader? Assuming the phone is encrypted, protected with a strong PIN code, developer mode and USB debugging options disabled, and there's an attacker who has physical access to the phone so he/she can boot the phone to bootloader or recovery interface using the special buttons.
Encryption should protect the user data, at least from unsophisticated attackers, but can the attacker install malicious software into the phone?
With an unlocked bootloader, does the phone respond to fastboot or ADB commands from a computer even if developer mode and USB debugging are disabled?
What is the difference if these options are disabled, the bootloader is locked and the "OEM unlock" option in the menu is also disabled?
Considering my possible phone upgrade in the far future, is there a phone that allows one to insert custom signing keys into the bootloader so that the bootloader could be kept locked while having a custom ROM? Or to flash an entirely custom bootloader with custom signing keys?

unlocked bootloader allows the modification of the partitions and access to your data from a custom recovery.

All I know is that an unlocked bootloader is easier to root as commands can be sent to the device using the fastboot protocol used to boot it so it is not necessary to take advantage of an exploit on the device in order to root it

Roizoulou said:
unlocked bootloader allows the modification of the partitions and access to your data from a custom recovery.
Click to expand...
Click to collapse
So a threat actor with physical access to the phone could then install malware using the recovery environment, without the user ever noticing it?
Encryption should protect the data but having malware in the phone would quickly compromise it.
Stephanie_Sy said:
All I know is that an unlocked bootloader is easier to root as commands can be sent to the device using the fastboot protocol used to boot it so it is not necessary to take advantage of an exploit on the device in order to root it
Click to expand...
Click to collapse
Hm, so this means that a phone with an unlocked bootloader will reply to fastboot commands from a computer even if developer/debug settings etc. are not enabled inside the main OS?

novabright said:
So a threat actor with physical access to the phone could then install malware using the recovery environment, without the user ever noticing it?
Encryption should protect the data but having malware in the phone would quickly compromise it.
Hm, so this means that a phone with an unlocked bootloader will reply to fastboot commands from a computer even if developer/debug settings etc. are not enabled inside the main OS?
Click to expand...
Click to collapse
1. yes
2. yes

Want to make a backup image of phone without root

I have a SM-A530W running Android 9 but is unrooted with a locked bootloader. I want to make as complete backup of the phone as possible, preferably using DD so I get a byte for byte image. Using OEM Unlock will wipe the device, so is there any way to flash a custom recovery or root the phone without wiping it? Or is there a way to get a full image of the device without root? I have full access to the phone with the PIN code and google account password.